Mobilized Tail Bearing Pumpjack

ABSTRACT

A pumpjack includes a walking beam pivotally connected to a vertical support for oscillation in a generally vertical plane about a first axis. A first end of the walking beam is connected to a sucker rod string. A carriage is movably mounted to the walking beam to move back-and-forth along a length of a tail end of the walking beam. A pitman arm has a first end pivotally connected to the carriage for rotation about a second axis and a second end pivotally connected to a crank arm. A counterweight is mounted to the crank arm and a hydraulic ram is connected to the carriage to move the carriage back-and-forth along the walking beam and establish reciprocation of the sucker rod string.

FIELD OF THE INVENTION

The present invention relates generally surface equipment for actuatinga pump mounted on a bottom end of a sucker rod string for pumping fluidfrom a well. More particularly, the present invention relates to amodified pumpjack construction that is operated to alternate an amountof counter weight exerted on a tail of a walking beam to maintain abalanced condition on the walking beam throughout an entire pump cycle.

BACKGROUND OF THE INVENTION

A pumpjack is a type of lever that is widely used to pump fluids fromwells. Pumpjacks of numerous constructions have been devised in anattempt to optimize the pumping efficiency and to reduce operating powerrequirements. Conventionally, a pumpjack includes a lever called awalking beam that is pivotally mounted at its center on a verticalsupport frame that is often referred to as a Samson post. The pumpjackis powered by a prime mover, such as a combustion engine or electricmotor, and operates to convert rotary motion of the prime mover intooscillating motion in the walking beam to reciprocate a rod string andpump to lift fluid from a well.

A pumpjack has many inherent problems. First, the weight exerted on thehead end of the walking beam varies during oscillation because the horsehead and the counter weight follow an arc and the bridle (connected tothe sucker rod string) must lift the weight on a vertical plane createdby the movement of the rod string inside the wellbore. With reference toFIG. 1, as the horse head falls below the horizontal it becomesexponentially heavier and as raises above the horizontal it becomesexponentially lighter, which is caused by moving the center of gravityexerted on the walking beam by the horse head and the bridle.

Second, the pumpjack counter weight is positioned in a fixed locationand requires shutting down the pumpjack to reposition the counterweight. Consequently, the counter weight is typically positioned suchthat the pumpjack operates in an unbalanced condition. The unbalancedcondition is related to the continuously varied weight on the head ofthe pumpjack caused by a myriad of varying wellbore conditions.

Due to the fact that a pumpjack operates to lift multiple thousands ofpounds, these incremental out of balances create sizable increases inoperating horsepower requirements. In practice, a pumpjack alwaysoperates in out of balance conditions and be must be over powered toovercome them. These out of balance conditions greatly decreaseoperating efficiency and increase operating costs, as well as, createundue stress on all the components which leads to premature failures ofthe pumpjack. Conversely, when operated in a balanced condition thehorsepower requirements are in the range of 0.01 horsepower per 1000 lbsof weight being lifted and the stresses on the pumpjack are reducedexponentially, as are the operating costs.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a modification to aconventional pumpjack that overcomes the problems discussed above andother inherent problems. In an embodiment, the modification includes amobilized tail bearing that is actuated by a hydraulic or electric ramto vary the distance from the fulcrum at which the counterweight acts onthe walking beam. Varying this distance provides the ability to operatethe pumpjack in a balanced condition at all times within a wide range ofweight drift. It also provides for maintaining a balanced conditionthroughout the entire reciprocating cycle when utilizing an existingprime mover and gearbox, thereby eliminating the inherent sine wave ofunbalanced force that is created by the swinging of the walking beam inan arc and the vertical movement of the rod string.

In another aspect, the present invention provides a newconventional-style pumpjack with a mobilized tail bearing actuated by ahydraulic or electric ram which can initiate the rotary motion of thecounterweight and the reciprocating motion of the walking beam utilizinggravity without the need for a gearbox or prime mover. The process ofinitiating motion from a balanced condition is easily achieved by overor under balancing the unit making it either head heavy or tail heavyand allowing gravity to act on the unit and overcome friction toinitiate motion.

And the inherent sine wave of unbalanced force that is created by theswinging of the walking beam in an arc and the vertical movement of therod string is regenerated back into the cycle of positioning andre-positioning the tail bearing.

In another aspect, the present invention includes a control system thatcontinually monitors sucker rod weight, thereby revealing operatingconditions related to the wellbore and the pumping equipment therebyproviding invaluable information to the operator.

In another aspect, the present invention, when embodied as a gravityactuated pumpjack, uses simple equipment and reduces overall complexityof a conventional pumpjack that is equipped with a gearbox and primemover. The rate of cycling can be accelerated or slowed based on fluidproduction, thereby continually optimizing daily production rateswithout equipment modifications. This can greatly reduce the number ofjack sizes and stroke lengths required at any given maximum productionrates to be achieved. As production rates diminish, the cycles per daycan be reduced while maintaining the cycle rate of travel at optimalrates in order to maintain pump efficiency.

Embodiments of the present invention can reduce overall operating costsby as much a 400% and extend equipment life cycles. Greatly extendedequipment live cycles and reduced operating costs will lower theeconomic limits of any given hydrocarbon production allowing for greaterultimate recoveries of a resource at any given sales price level.

Embodiments of the present invention provide a modified pumpjackconstruction for producing fluid from a well that is able to maintain abalanced condition between the head and the tail over a specified rangeof varying weight and friction encountered in the wellbore. Specificrange is established by the amount of static weight bolted to the crankarms and the weight mounting position on the crank arms relative to thecrank pin, both of which are mechanically adjusted at time of initialinstall and when an out of range condition is flagged by the controlsystem.

Embodiments of the present provide a modified pumpjack construction forproducing fluid from a well that is able to initiate cycling of thepumpjack utilizing the effects of gravity by oscillating from a balancedcondition to a head heavy then tail heavy condition or vice versa.Energy input requirement to initiate motion from a balanced condition isextremely low, on the order of 0.01 hp/ton of weight, greatly reducingoperating costs. Acting from a balanced position greatly reduces thestress on all components and reduces maintenance costs and safetyissues.

Embodiments of the present provide a modified pumpjack construction forproducing fluid from a well that is able to sense fluid level in theannular space of a wellbore by comparing the position of the tailbearing in a balanced position from one cycle to the next. Fluid abovethe pump intake will create buoyancy in the tubing string causing thehead end of the pumpjack to become lighter. Pumpjack can start, balance,sense fluid level, cycle until buoyancy is eliminated, shutdown. If nofluid level is detected the pumpjack will shutdown after balancing.

Embodiments of the present provide a modified pumpjack construction forproducing fluid from a well that is able to initiate motion from a stopposition when crank arms are hanging vertically (tail heavy) and headweight is attempting to pull straight up on the centerline of the crankpin.

Embodiments of the present provide a modified pumpjack construction forproducing fluid from a well that is able to accelerate the cycling ofthe pumpjack until a “floating rod string” condition is encountered andthen slow the cycling to just below this point thus optimizing themaximum pumping capacity at any given stroke length. This greatlyimproves the range of production capacity of a given jack size greatlyreducing the number of jack sizes, stroke lengths and operating speedsrequired throughout the lifecycle of a wellbore. This action alsodramatically improves the efficiency of the downhole insert pump even atvery low daily production rates.

Embodiments of the present provide a modified pumpjack construction forproducing fluid from a well that eliminates the need for a gearbox andassociated external prime mover, motion is initiated by gravity actingon the walking beam. This greatly reduces the cost and complexity ofmanufacture and maintenance.

Embodiments of the present provide a modified pumpjack construction forproducing fluid from a well that is able to detect a wide range ofequipment failures by sensing friction and weight throughout the entirerotating cycle. Pump failures and efficiency issues, rod stringfailures, production tubing failures, bearing failures etc. can all bedetected and reported to the control system which is compatible with alland any new communication systems available now and in the future. Usingthis physical method of operation and control system in effect can makethe pumpjack “Smart”.

In an embodiment, a pumpjack for producing fluid from a well includes awalking beam pivotally connected to a vertical support for oscillationin a generally vertical plane about a first axis. A first end of thewalking beam is connected to a sucker rod string. A carriage is movablymounted to the walking beam to move back-and-forth along a length of atail end of the walking beam. A pitman arm has a first end pivotallyconnected to the carriage for rotation about a second axis and a secondend pivotally connected to a crank arm. A counterweight is mounted tothe crank arm and a hydraulic ram is connected to the carriage to movethe carriage back-and-forth along the walking beam and establishreciprocation of the sucker rod string.

There has thus been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thereofthat follows may be better understood and in order that the presentcontribution to the art may be better appreciated.

Numerous objects, features and advantages of the present invention willbe readily apparent to those of ordinary skill in the art upon a readingof the following detailed description of presently preferred, butnonetheless illustrative, embodiments of the present invention whentaken in conjunction with the accompanying drawings. The invention iscapable of other embodiments and of being practiced and carried out invarious ways. Also, it is to be understood that the phraseology andterminology employed herein are for the purpose of descriptions andshould not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception,upon which this disclosure is based, may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present invention.

For a better understanding of the invention, its operating advantagesand the specific objects attained by its uses, reference should be hadto the accompanying drawings and descriptive matter in which there areillustrated preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings illustrate by way of example and are included toprovide further understanding of the invention for the purpose ofillustrative discussion of the embodiments of the invention. No attemptis made to show structural details of the embodiments in more detailthan is necessary for a fundamental understanding of the invention, thedescription taken with the drawings making apparent to those skilled inthe art how the several forms of the invention may be embodied inpractice. Identical reference numerals do not necessarily indicate anidentical structure. Rather, the same reference numeral may be used toindicate a similar feature of a feature with similar functionality. Inthe drawings:

FIG. 1 is a diagrammatic illustration of the difference between arc ofthe beam and arc the bridle of a pumpjack, illustrating areas ofinherent imbalance;

FIG. 2 is a diagrammatic view of a pumpjack constructed in accordancewith the principals of an embodiment of the present invention;

FIG. 3 is a diagrammatic end view of a carriage and walking beam of thepumpjack illustrated in FIG. 2;

FIG. 4 is an enlarged, diagrammatic partial side view of the carriageand walking beam illustrated in FIG. 3;

FIG. 5 is an enlarged, diagrammatic partial side view of the walkingbeam and a saddle bearing spacer of the pumpjack illustrated in FIG. 2;

FIG. 6 is a block diagram of an exemplary control system of the pumpjackillustrated in FIG. 2; and

FIG. 7 is a diagram illustrating power regeneration (conservation)operation of a pumpjack in accordance with embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 2 through 5, there is representatively illustrated apumpjack 10 that is constructed in accordance with the principals of anembodiment of the present invention. The pumpjack 10 includes a walkingbeam 12 that is pivotally connected to a vertical support 14 by a saddlebearing 16 so that the walking beam is able to oscillate in a generallyvertical plane about the saddle bearing's rotation axis, similar to aconventional pumpjack. A horse head 18 is connected to front end 20 ofthe walking beam 12. And the horse head 18 is connected to a sucker-rodstring 22 in a conventional manner by a bridle 24.

A carriage 26 is movably mounted to the tail end 28 of the walking beam12 to move back-and-forth along a length of tail end 28. A tail bearing30 is mounted to a lower end of the carriage 26 is pivotally connects anend of a pitman arm 32 to the carriage to rotate about the tailbearing's rotational axis. The opposite end of the pitman arm 32 ispivotally connected to a crank arm 34 and the crank arm is rotatablyconnected at one end to a vertical support 36. A counterweight 38 isattached to the opposite end of the crank arm 34.

A hydraulic ram 40 is mounted, for example, to the walking beam 12 andincludes an extensible shaft 42 that is connected to the carriage 26.

As discussed further below, the hydraulic ram 40 operates to move thecarriage 26 back-and-forth along the walking beam 12 by extending andretracting the extensible shaft 42. In an embodiment, the carriage 26 ismovable equal distances on opposite sides of a centerline 44 thatextends substantially vertically from the pivot or bearing connectingthe crank arm 34 and vertical support 36. Further, the rotational axisof the tail bearing 30 and the saddle bearing 16 are disposed on acommon centerline 46 that extends between the two bearings. In anembodiment, the tail bearing 30 and the saddle bearing 16 are positioneda same distance from the bottom of the walking beam 12. Thesearrangements, as will become apparent, permit certain operation of thehydraulic pump 10.

In the illustrated embodiment, the hydraulic ram 40 is mounted to asaddle spacer 56 that is disposed between the saddle bearing 16 and thewalking beam 12. Saddle spacer 56 is sized so as to align centerline 46generally horizontal along the bottom of the walking beam 12. And atinitial setup, the walking beam 12 is balanced with the carriage 26positioned so that the tail bearing 30 is located on the centerline 44of the crank arm 34.

Alternatively, the hydraulic ram 40 could be replaced by an electricallypower operator to move the saddle bearing along the walking beam in themanner discussed above.

As best seen in FIGS. 3 and 4, and in an embodiment, the walking beam 12is an I-beam and the carriage 26 is movably mounted to the bottom flangeof the I-beam by a system of rollers. Particularly, the carriage 26includes two pairs of running wheels 48 and 50, one pair disposed alongeach side of the carriage and in rolling contact with a top surface ofthe bottom flange of the walking beam. Additionally, carriage 26includes two pairs of up-stop wheels 52 and 54, one pair disposed alongeach side of the carriage and in rolling contact with a bottom surfaceof the bottom flange of the walking beam 12. The running wheels 48 and50 bear the weight of the carriage 26 on the walking beam 12 and theup-stop wheels 52 and 54 prevent the carriage from coming up off thewalking beam.

Further illustrated in FIG. 3, carriage limit stops 56 (only one isillustrated, the other is positioned on the opposite side) are mountedto the walking beam 12 to limit the carriage's forward travel along thewalking beam. In an aspect, each limit stop 56 is wedge shaped and taperfrom narrow to wide in a direction from the tail toward the front of thewalking beam and has a positive stop at the wide end. In an over travelcondition, the limit stops 56 wedge between the up-stop wheels 52 and 54and the walking beam 12 to prevent forward movement of the carriage.

Also illustrated in FIG. 4 is a carriage lock 58 that includes astructure 60 mounted to the walking beam 12, a corresponding structure62 mounted to the carriage 12, and a pin or bolt 64 that can be insertedthrough apertures in structures 60 and 62 so as to lock the position ofthe carriage along the walking beam.

Referring to FIG. 6, there is diagrammatically illustrated an exemplarycontrol system 66 for operating the hydraulic pumpjack 10. Controlsystem 66 included a programmable logic controller (PLC) 68, a hydraulicram position sensor 70, a beam position sensor 72, a load sensingproportional valve 74, and a valve actuator 76. The hydraulic ramposition sensor 70 is operatively connected to the hydraulic ram 40 andoutputs a signal that is indicative of the position of the ram'sextensible shaft 42. The beam position sensor 72 is operativelyconnected to the walking beam 12 and outputs a signal that is indicativeof the position of the walking beam. The load sensing proportional valve74 operates to determine the load on the hydraulic ram and output asignal that is indicative of this sense load. The load sensingproportional valve 74 is also hydraulically connected to the hydraulicram 40 and is operated by valve actuator 76 to control the hydraulicram.

The PLC 68 is electrically connected to the hydraulic ram positionsensor 70, the beam position sensor 72, the load sensing proportionalvalve 74, and the valve actuator 76. The PLC operates the valve actuator76 as a function of the signals received by the hydraulic ram positionsensor 70, the beam position sensor 72, and the load sensingproportional valve 74 to move the carriage 26 back-and-forth along thewalking beam to drive the pump and reciprocate the sucker rod string.

Generally, reciprocation of the sucker rod string is accomplished usinggravity by alternating the balance of the walking beam 12 between a tailheavy condition and a head heavy condition by moving the carriage 26back-and-forth along the walking beam 12, which positions counterweight38 to create either the tail heavy or head heavy condition.

With reference to FIG. 7, the pumpjack 10 is able to regenerate powerthroughout rotation of the counter weight crank arms, which isillustrated in four separate quadrants of rotation. Starting withquadrant one, the head is down and the pumpjack is head heavy. Thecarrier moves rearward causing the pumpjack to be tail heavy and tostart lifting the head to horizontal (9:00 position). The bridle movesback to arc of head as the crank approaches horizontal (9:00 position),thereby making the pumpjack head light.

Continuing in quadrant two, the head is horizontal and weight on thebridle is following arc of the head, the head becomes lighter as thecrank arms fall vertical (6:00 position). The carrier moves forward toshift from tail heavy to head heavy.

Continuing in quadrant three, the head is upward carrier moves forwardto locate balance point (3:00 position) with the beam on the horizontalplane.

In quadrant four, the head falls below the horizontal, the bridle swingsaway from the beam, the head increasingly becomes heavy, and the crankarms accelerate (between 3:00 and 12:00 position). The carrier movesrearwardly to shift from head heavy to tail heavy.

Input energy required in quadrant three and one to move the carrier,crank arms accelerating in quadrant two. Inertia generated in quadranttwo is conserved in quadrant three, so the more inertia gained inquadrant two (speed of rotation+unbalance), the deeper into quadrantthree the crank arms will rotate. Therefore, less work is required inquadrant three to move the carrier to the balance point. Energy causedby unbalance in quadrant two is regenerated (conserved) into quadrantthree. The same principal occurs between quadrants one and four.Further, inherent unbalance caused by the bridle arc is regenerated intoinput side of energy requirement.

The PLC 68 can be programmed to perform many different operations,several operations are discussed below.

1. Maintenance Shut Down (ESD).

In this mode, the PLC 68 operates the hydraulic ram 40 to move thecarriage 26 to the most rearward position, e.g., by fully extending thehydraulic ram so the pumpjack is maximum tail heavy and crank arm 34 isdisposed at the 6 o'clock position. Indication is given to the operatorto install carriage lockout pin and positive lock the crank arms. ESDthe hydraulic supply. Await operator reset commands.

2. Travel to Park Position.

In this mode, the PLC 68 operates the hydraulic ram 40 to move thecarriage 26 forwardly along the walking beam toward the saddle bearing16 until the crank arm 34 moves counter-clockwise to the 1 o'clockposition. In this position, the walking beam 12 is head down and thepitman arm 32 is parallel to the crank arm 34. The pumpjack 10 is placedin this position when it shutdown to protect the sucker-rod string andpolish rod inside the wellbore. Further, operation of the pumpjack 10 ismost easily started from this position.

3. Balance.

In this mode, and from the park position, the PLC 68 operates thehydraulic ram 40 to move the carriage 26 is rearward along the walkingbeam 12 until the crank arm 34 rotates in a clockwise direction andstabilize in the 3 o'clock position. (When the unit is first installedthe physical weights are adjusted on the crank arms so that the fullstring weight and a full column of fluid with no fluid below the pumpare balanced with the centerline of the tail bearing carrier on thecenterline of the crankshaft).

4. Check for Fluid Level.

In this mode, the PLC 68 operates to determine if the balance pointdetermined in #3 above is forward of the crankshaft centerline itindicates that fluid has entered the wellbore in the annular spaceoutside the production tubing. This will create buoyancy in the tubingstring and make the pumpjack lighter at the head end. If no fluid isdetected the pumpjack will shut down and go back to the park position #2above.

5. Swab Well.

In this mode, the PLC 68 is operates the hydraulic ram 40 to alternatemoving the carriage 26 forward and rearward causing the pumpjack 10 tooscillate at a set speed. The pumpjack 10 can run in this configurationuntil the balance point has moved back to the centerline of thecrankshaft (indicating a pumped off condition), at which time, the PLCwill operating the park position mode. On a gas well that makes water,the jack can be instructed to swab by the external gas flow chartdifferential as well.

6. Produce Well at Maximum Production Rate.

In this mode, the PLC 68 operates the hydraulic ram 40 to move thecarriage 26 back-and-forth along the walking beam 12 to acceleraterotation of the walking beam until the sucker-rod string starts to float(hydraulic ram will see the floating if the rate begins to exceedbuoyancy or friction factors present in the well). This is the maximumproduction rate possible with the least amount of energy expended. Ifthe pumpjack 10 cannot attain this condition then the PLC instructionsthe operator to lengthen the stroke or in an extreme case require thewell to be equipped with a bigger jack. This feature will allow themanufacture of the pumpjacks to reduce the number of jack sizes offeredas the production rates attainable with any given stroke length can beoptimized. The PLC is capable of learning to slow down pumping as thewell approaches pumped off conditions and speed up to optimizeproduction rates.

7. Conduct Wellbore Diagnostics.

At all times during operation, the PLC 68 can detect wellboreconditions, pump efficiency, holes in production string, leaking travelballs, broken rods, tight packings, etc. by monitoring pressure balancesacross the hydraulic ram 40. The pumpjack 10, in essence, becomes itsown dynamometer. The PLC 68 can easily be tied to SCADA control or evenmonitored with a mobile computing device.

A number of embodiments of the present invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims. Preliminary Amendment

1. A pumpjack for lifting fluid in a well bore, the pump comprising: awalking beam pivotally connected to a vertical support for oscillationin a generally vertical plane about a first axis, a first end of saidwalking beam connected to a sucker rod string; a carriage movablymounted on a bottom of said walking beam for movement back-and-forthbelow the walking beam along a length of a tail end of said walkingbeam; a pitman arm having a first end pivotally connected to a bottom ofsaid carriage for rotation about a second axis and a second endpivotally connected to a crank arm; a counterweight mounted to the crankarm; and a hydraulic ram connected to said carriage beneath the walkingbeam for moving said carriage back-and-forth along said walking beam andestablish reciprocation of the sucker rod string.
 2. The pumpjack ofclaim 1, wherein said first and said second axis is disposed verticallybelow said walking beam.
 3. The pumpjack of claim 3, wherein said firstand said second axis are disposed along a common centerline that extendsbetween said first axis and said second axis.
 4. The pumpjack of claim1, wherein said carriage is movable equal distances on opposite sides ofa crank arm centerline that extends substantially vertical from a pivotconnection between the crank arm and a second vertical support.
 5. Thepumpjack of claim 1, further comprising: one or more carriage stopsmounted to said walking beam.
 6. The pumpjack of claim 1, furthercomprising: a programmable logic controller, a hydraulic arm positionsensor operatively connected to said hydraulic ram to determine theposition of an extensible shaft of said hydraulic ram and output ahydraulic ram position signal that is indicative of the determinedposition of the extensible shaft; a beam position sensor operativelyconnected to said walking beam to determine the position of said walkingbeam and output a beam position signal that is indicative of thedetermined position of said walking beam; a load sensing spool valveoperatively connected to said hydraulic ram to determine a load on saidhydraulic ram and output a load signal that is indicative of thedetermined load on said hydraulic ram, said load sensing spool valvehydraulically connected to said hydraulic ram; a valve actuatoroperatively connected to said load sensing spool valve; said PLCelectrically connected to said hydraulic arm position sensor to receivesaid hydraulic ram position signal, electrically connected to said beamposition sensor to receive said beam position signal, electricallyconnected to said load sensing spool valve to receive said load signal;and said PLC programmed to operate said valve actuator based on saidhydraulic ram position signal, said beam position signal, and said loadsignal to cause said hydraulic ram to move said carriage back-and-forthalong said walking beam.
 7. The pumpjack of claim 6, wherein said PLC isprogrammed to perform a maintenance shut down operation.
 8. The pumpjackof claim 6, wherein said PLC is programmed to perform a travel to parkposition operation.
 9. The pumpjack of claim 6, wherein said PLC isprogrammed to perform a balance operation.
 10. The pumpjack of claim 6,wherein said PLC is programmed to perform a check for fluid leveloperation.
 11. The pumpjack of claim 6, wherein said PLC is programmedto perform a swab well operation.
 12. The pumpjack of claim 6, whereinsaid PLC is programmed to perform a produce well at maximum productionrate operation.